The result of a referendum on whether the Welsh Government should be able to vary income tax rates up or down would be too close to call, according to an exclusive poll for the Western Mail.

Last month Prime Minister David Cameron and his Deputy Nick Clegg announced that Westminster would legislate so that such a referendum could take place after 2015, but the decision on whether and when it should occur will be left to AMs.

The UK Government would like to see a referendum in 2017, with implementation in 2020 if there is a Yes vote. Mr Cameron and Mr Clegg take the view that it would be appropriate for the Welsh Government to raise some of its own revenue.

The poll – undertaken for us by Cardiff-based Beaufort Research – showed that 32% of voters would back such a power being devolved to Wales, with 30% against. Some 19% said they would not vote while a further 17% said they didn’t know. 1% of the sample were too young to vote. The figures do not add up to 100% because of rounding.

There are significant differences in voting intention according to region, gender, age, social class and whether people can speak Welsh or not, the poll shows.

Those living in North Wales were most likely to support a Yes vote (by 39% to 28%), while those living in Cardiff and South East Wales were most likely to back a No vote (by 32% to 23%).

All three other regions showed a relatively modest preference for a Yes vote (by 37% to 32% in Mid and West Wales, 32% to 29% in West South Wales, and 33% to 31% in the Valleys).

Men were less enthusiastic about the proposal than women, with 36% saying they would vote No against 32% who said they would vote Yes. Women backed a Yes vote by 33% to 25%.

In terms of age, the most support for income tax varying powers was found among 25-34 year-olds, with 41% saying they would vote Yes and 18% No.

Those aged over 65 showed the biggest majority against the proposal – by 40% to 31%.

Those aged between 16 and 24 were also more likely to vote No than Yes (by 25% to 20%), but there were more in that age group who either didn’t know how they would vote or wouldn’t vote at all.

Those aged between 35 and 44 backed a Yes vote by 37% to 24%, while those aged between 45 and 54 backed a No vote by 33% to 30%. Those aged between 55 and 64 favoured a Yes vote by 38% to 36%.

Those in the managerial and professional AB class would split 39% Yes to 40% No. Those in the skilled C1 category would back a Yes vote by 36% to 34%, while semi-skilled people in the C2 class would favour a No vote by 33% to 31%. Unskilled and unemployed people in the DE category would split 28% Yes to 22% No.

Welsh speakers are more likely to back a Yes vote (by 39% to 26%), while those who cannot speak the language narrowly favoured a No vote by 32% to 30%.

First Minister Carwyn Jones has responded cautiously to the offer of a referendum, saying he does not think one would be appropriate until Wales has secured “fairer funding” from Westminster. According to a commission of economic experts who reported three years ago, the current Barnett Formula results in Wales receiving at least £300m a year less than it would do if the allocation was based on social need.

A Welsh Labour spokesperson said: “This poll underlines the common sense approach being taken by the Welsh Labour Government. It would be irresponsible to commit to a referendum before the issue of fair funding is resolved, and it is likely that a vote in the immediate future would be lost.

“That is in no-one’s best interests.”

A Welsh Conservative spokesman said: “The UK Government’s decision to allow a referendum on income tax is extremely significant and shows the Conservative-led coalition’s commitment to Wales.

“This a question that must now be put to the people of Wales and we continue to urge Labour’s First Minister to work towards a referendum.

“Welsh Conservatives are committed to being the low tax party of Wales, keeping more of people’s money in their pockets and allowing us to grow the Welsh economy.”

“The results are encouraging for those of us that want Welsh democracy to continue to develop and improve.

“However, taken together with other recent polls we know that while a referendum could be won, support is finely balanced.

“Plaid Cymru has been frustrated that the model of income tax being offered to Wales is not what the Silk and Holtham Commissions recommended.

“We need to look at the link between borrowing and investment, and having a ‘Yes’ vote in a referendum.

“There may well be a strong case for a Yes vote based on the prospect of unlocking extra investment powers, which could see us being able to put more capital expenditure into infrastructure, road and rail, schools and hospitals.

“We will also be pressing current and future Westminster Governments to remove the so-called ‘lock-step’ clause that makes the income tax powers less useful. Plaid Cymru is ready to put Wales first and make the positive case for these powers.”

Welsh Liberal Democrat finance spokesman Peter Black said: “It is pleasing to see that there is support for Wales to have powers to vary income tax.

“However, there is certainly no clear majority and it is only natural for many people not to have decided how they would vote.

“This highlights how essential it will be for all parties to work together on this issue, much like we did in the 2011 referendum. Tax varying powers would mean that, for the very first time, the amount of money a Welsh government spends could be directly linked to success in promoting economic development.

“Nearly all other national parliaments have this power, as indeed do community councils, and the Welsh Liberal Democrats believe that Wales should be no different.

“With the Liberal Democrats as part of a Coalition government, we are the driving force behind radical change.

“Devolution is now moving at a pace it hasn’t seen before. In just three years, the Liberal Democrats have achieved a referendum on law making powers and are now delivering further powers by implementing the Silk Commission’s key recommendations.

“These new powers will give Wales the opportunity to improve its economy whilst giving people more of a say over how they are governed.”

Beaufort Research interviewed a representative sample of 1,022 over-16s living in Wales. Most of the fieldwork was done between November 15 and November 26, with the remainder the following week.